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Revised theory of gravity doesn’t predict a Big Bang

Taking as a starting point what is a very old idea of the beginning of the Universe as an alternative for General Relativity and the Big Bang theory, Astrophysicists Máximo Bañados from Universidad Católica de Chile and Pedro Ferreira from University of Oxford have resurrected a theory from the early 20th century that has a very interesting property of not having singularities.

They have reconsidered the theory of gravity proposed by Arthur Eddington who in 1924 proposed a “gravitational action” — the mechanism that describes how gravity can emerge from space-time being curved by matter and energy — which could serve as an alternative starting point to general relativity. However, it only worked for empty space and didn’t include any source of energy such as matter, making it an incomplete theory.

Ever since scientists have attempted various ways of including matter into the theory unsuccesfully. In this study, Banados and Ferreira have tried a new way to extend the theory to include matter by using a gravitational action called the Born-Infeld action.

They found that a key characteristic of Eddington’s theory is that it reproduces Einstein gravity precisely in the vacuum conditions, but it produces new effects when matter is added, bringing implications especially for high-density regions, such as in the very early Universe or within a black hole.

More intriguingly, the theory could lead to an entirely new view of the Universe that doesn’t include a singularity such as a ‘Big Bang’ in early times, meaning that it was once infinitely small. Eddington’s revised theory requires a minimum length of space-time at early times, which means that the Universe could not have been a singularity.

The theory predicts that the Universe may have loitered for a long time at a relatively small size before growing large enough to be controlled by standard cosmological evolution. Another possibility is that the Universe could have undergone a bounce, resulting from the collapse of a previous Universe. Any kind of singularity-free Universe would solve the singularity problem that has bothered scientists about general relativity, since a singularity cannot be mathematically defined.

In the future, the researchers hope to perform a more detailed analysis of the gravitational Born-Infeld action. The theory is still in the early conceptual stages, and has a long way to go before they know how accurate it is.

Source: PhysOrg.com | The paper is available via Physical Review Letters and arXiv.org